1. Field of the Invention
This invention relates generally to a voice messaging system. More particularly, it relates to a voice messaging system such as a telephone answering device which is capable of allowing a user to retrieve deleted messages.
2. Background of Related Art
Voice messaging systems (e.g., telephone answering devices (TADs)) are useful devices for both the home and office. Larger voice messaging systems in general work in conjunction with a private branch exchange (PBX) unit to provide voice mailboxes for a large number of users. Smaller voice messaging systems, e.g., telephone answering devices typically operate on a single telephone line and answer an incoming call to an unused (i.e., on-hook) telephone after a predetermined number of rings.
Voice messaging systems and telephone answering devices cause a telephone line to enter an off-hook condition, then play an outgoing greeting message to the caller. After the outgoing greeting message is completed, the caller is allowed to record a voice message on the voice messaging system, e.g., telephone answering device. At a later time, the voice message is replayed by the user, either local to the telephone answering device or via remote connection from another telephone through the public switched telephone network (PSTN).
FIG. 4 illustrates a conventional telephone answering device capable of answering an incoming call on a telephone line.
In FIG. 4, a telephone answering device 11 is connected to a telephone company central office 13 via a telephone line 15. A telephone line interface (TLI) 17 in the telephone answering device 11 provides the conventional isolation, DC and AC impedance as required by telephone company standards. The telephone line interface 17 also provides a ring detect signal to a controller 19. The controller 19 can be any suitable processor, e.g., microprocessor, microcontroller, or digital signal processor (DSP). The ring detect signal indicates to the controller 19 the ringing of an incoming call on the telephone line 15.
After a predetermined number of ring signals typically set at the voice messaging system or telephone answering device, the telephone answering device 11 causes the telephone line interface 17 to place the telephone line in an off-hook state. A voice recorder/playback module 21 plays an outgoing greeting message over the telephone line 15 to the caller. Upon completion of the outgoing greeting message, the caller may record a voice message in voice message memory 23 under the control of the controller 19 and through the voice recorder/playback module 21. A keypad 25 allows the user to select various modes of operation, including the playback of voice messages, and the deletion of certain voice messages.
In some instances, either before reviewing the voice message, during the review of the voice message, or subsequent to reviewing the voice message, the user may either accidentally or intentionally delete a particular voice message from the telephone answering device 11 that they later wish they hadn't deleted. While the conventional telephone answering device 11 allows a user to review recorded voice messages as many times as desired before deletion, if a voice message is deleted, either accidentally or intentionally, the voice message is no longer accessible for review by the user, and is erased from the voice message memory 23.
Accordingly, there exists a need for an improved voice messaging system and technique which allows a user to retrieve deleted voice messages.